Many-Body Contribution to Self-Diffusion in Rare-Gas Solids

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Abstract
The formation and self-diffusion activation energies for single vacancies and divacancies in solid argon are calculated including contributions due to triple-dipole interactions. The triple-dipole interactions lower both the formation and activation energies relative to the values calculated with a pair potential only. The calculated activation energies, 3307 cal/mole for single vacancies and 4192 cal/mole for divacancies, are in equally good agreement with the recent experimental results, 3600-3900 cal/mole. The calculated energy of formation of a vacancy, 1790 cal/mole, is in poor agreement with the value of 1270 cal/mole estimated by corresponding states from krypton experimental data. Consideration of Jansen superexchange forces and four-dipole interactions lowers the vacancy formation energy to ∼1430 cal/mole and the divacancy self-diffusion activation energy to ∼3510 cal/mole. The agreement between calculated and experimental values of the vacancy formation energy and activation energy (for divacancy diffusion) suggests that self-diffusion in rare-gas solids may occur via divacancies at high temperatures.

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